1) Field of the Invention
The field of the present invention relates generally to monitoring devices and methods and, more particularly, to devices and methods for monitoring water depth and other aspects of sewers, storm drains, waterways, and the like.
2) Background
Most municipalities have a sanitary wastewater system, the purpose of which is to collect and transport waste matter from the various drains, disposals and other sources within the community to a sewage treatment plant or other such facility. Ideally, the waste matter is transported via the sanitary wastewater system without any spillage or leakage whatsoever. However, sanitary wastewater systems can be enormous in scale, making their management and maintenance extremely challenging tasks. Even in smaller municipalities, managing and maintaining the local sanitary wastewater system can be difficult. Problems often arise from the demands placed upon these systems, which may be found in widely varying states of repair. Such demands generally include severe weather conditions (such as heavy rains or freezing temperatures), accumulation of obstructive materials (e.g., grease, sediment, roots or other debris), and groundwater infiltration, to name a few. In addition, community growth, either industrial or residential, can lead to increased strain on an existing sanitary wastewater system. When the wastewater collection system becomes taxed beyond capacity, manhole overflows and/or backflow into residential areas may result.
The adverse conditions preceding an overflow (or other similar event) often exist over an extended period of time (usually several days or weeks), gradually worsen, and, if not detected and rectified, cause the inevitable result. During the time preceding such an overflow event, wastewater begins to accumulate in one or more localized areas within the collection system, until gradually the level of the wastewater becomes so high it breaches the nearest outlet—usually a manhole opening—or else backs upstream where further problems can be caused.
A sewer overflow can pose significant health hazards within a local community. The cleanup operation can be costly, and an overflow can bring about an interruption in sewer service. Also, a sewer overflow can harm the local environment, and result in potential state and/or federal penalties.
To reduce the likelihood of overflow and backflow events, it has been common practice to place flowmeters at various points within the wastewater collection system, thereby allowing the liquid flow within the system to be monitored. Often the flowmeters are placed at locations where access is convenient, such as in sewer manholes.
A variety of different flowmeters have been developed, a number of which have been used or proposed for use in a wastewater monitoring system. One common class of flowmeters has a “primary” element and a “secondary” element. The primary element is a restriction in a flow line that induces a differential pressure and/or level, and the secondary element measures the differential pressure and/or level, converts the measurements into a flow rate, and records the flow rate data. Weirs and flumes are some of the oldest and most common devices used as flowmeter primary elements. More recently, flowmeters have been developed which use ultrasonic pulses to measure the liquid level, which is then converted into a flow rate.
A variety of drawbacks exist with conventional flowmeter monitoring systems. First, many flowmeter installations are configured to provide manual reading of the flow data that has been acquired over time. Reading the flow meter data can be a burdensome task. Generally, a field worker is required to travel to the physical location of the manhole, pry off the manhole cover, descend into the manhole, and attempt to collect the data from the secondary element of the installed flowmeter. Where numerous flowmeters are installed throughout a large municipal wastewater collection system, the task of collecting flow data from all of the flow meters can be a time-consuming, labor intensive (and therefore expensive) process. In situations of sudden rainfall events or other circumstances, it can be very difficult for field workers to monitor all of the flowmeters in the system, and a risk of overflow increases.
In addition to the difficulty in obtaining flow data from flowmeters installed in a wastewater collection system, flowmeters can also be expensive, and often require a high level of accuracy that can be difficult to maintain over time. Inaccurate liquid flow measurements in the context of a wastewater collection system can lead to serious or even disastrous results. Flowmeters may also require periodic inspection and cleaning, and can therefore be relatively expensive to maintain.
Various types of sewer monitoring systems have been developed or proposed to alleviate the need for manual data collection. One example is illustrated in U.S. Pat. No. 5,608,171 to Hunter et al. However, available sewer monitoring systems of the wireless variety generally require devices that are expensive or require expensive components, can be difficult to install or remove, and/or have limited functionality or compatibility with other equipment.
It would therefore be advantageous to provide an improved technique for monitoring sewers, storm drains, waterways, and other such areas, to prevent overflows, facilitate maintenance, and improve information available for municipal planning purposes.